coremem_types: enum: verify that setting the discriminant works as expected

crates/types/src/compound/enumerated.rs

@@ -27,10 +27,15 @@ impl<P: Peano> DiscriminantCodable<P> for Discr<P> {
 }
 
 impl<P: Peano> Discr<P> {
+    pub fn new(u: u32) -> Self {
+        assert!(u < P::VALUE);
+        Self::new_unchecked(u)
+    }
     fn new_unchecked(u: u32) -> Self {
         Self(u, Default::default())
     }
 }
+
 impl<P: Peano> Discr<P> {
     fn dispatch<H: DiscrHandler<P, O>, O>(&self, h: H) -> O {
         match self.0 {
@@ -153,17 +158,22 @@ mod test {
     use super::*;
     #[test]
     fn dispatch() {
-        struct Receiver {
-            returns: f32,
-        }
-        impl<P: Peano, T> VariantHandler<P, T, f32> for Receiver {
-            fn call(&self, _: T) -> f32 {
-                self.returns
+        struct Receiver;
+        impl<P: Peano, T: TryInto<i32>> VariantHandler<P, T, i32> for Receiver {
+            fn call(&self, v: T) -> i32 {
+                unsafe {
+                    v.try_into().unwrap_unchecked() + P::VALUE as i32 + 5
+                }
             }
         }
 
-        let e: Enum<(Discr<P2>,), List<(u32, f32)>> = Enum::default();
-        let r = Receiver { returns: 5f32 };
-        assert_eq!(e.dispatch(r), 5f32);
+        let mut e: Enum<(Discr<P3>,), List<(u32, i32, u8)>> = Enum::default();
+        assert_eq!(e.dispatch(Receiver), 5);
+
+        e.encode_discr(Discr::new(1));
+        assert_eq!(e.dispatch(Receiver), 6);
+
+        e.encode_discr(Discr::new(2));
+        assert_eq!(e.dispatch(Receiver), 7);
     }
 }